The present invention relates to catheters in general, and more particularly to implantable arterial catheters, especially multidose injection catheters.
There are already known various constructions of catheters, among them such which include a multidose injection receptacle which has a shell that bounds a chamber with an open end and is provided with a fastening flange, and a pierceable diaphragm which spans and seals the open end of the chamber and thus separates the chamber from the exterior of the multidose injection receptacle. A catheter tube has one end portion which is connected to the multidose injection receptacle and communicates with the chamber, and another end which is remote from the multidose injection receptacle and carries a safety valve.
In a typical construction of the catheter of the above type, the safety valve is constituted by the other end portion of the catheter tube which is closed and is provided with lateral flow orifices, and a protective cap which is slid onto this other end portion of the catheter tube. In this catheter construction, the pressure of the fluid being administered to the catheter recipient through the chamber of the injection receptacle and through the catheter tube expands the protective cap at the region of the lateral flow orifices of the other end portion of the catheter tube and, in this manner, the fluid can flow out of the safety valve and into the bloodstream of the recipient. Experience with safety valves of this type has shown, however, that they leave much to be desired in terms of reliability and especially prevention of return flow of fluid into the safety valve or even into the catheter tube, with attendant clogging and other problems.